1. Field of the Invention
This invention relates to agricultural tillage tools, and more particularly to plow chisels which carry a leading point at the forward, lower end of an elongated shank, and are used in cultivating the soil.
2. Brief Description of the Prior Art
For the purpose of protecting the earth-penetrating portions of various types of tillage tools from abrasive wear, thereby extending the effective service life of such tools, several techniques have been used to afford such protection. In one of these an overcap point or protective plate has been mounted upon the lower, leading end of the tillage tool, so that the portion of the tool which first contacts the soil in a breaking action is protected against abrasion by the use of such an overcap or tip located in a protective position. Such overcaps or tips secured to the forward end of the shank of the tool have heretofore, in many instances, been made of a hard metal, such as tungsten or chromium carbide, and such overcaps or protective elements have been secured to the tillage tool shank either by welding or by a mechanical interlock.
Examples of prior art tillage tools which have been made up in this way are those which are illustrated and described in U.S. Pat. Nos. 4,363,354 to Wetmore; 1,095,404 to Koepke; 4,408,667 to Jarvis; 4,529,042 to Wetmore; 4,457,381 to Wetmore ; 4,269,274 to Robertson et al; 3,082,555 to Hill; 750,385 to Naidul and 989,729 to Swindle.
In U.S. patent application Ser. No. 706,128 entitled "TILLAGE TOOL", of which the present application is a continuation-in-part, I have described a protective point or insert which is utilized to protect the leading end of a tillage tool shank, and which is engaged with the shank by means of a key which interfits in a dove-tailed slot formed in the pointed forward end of the shank. The point can easily be intentionally removed if desired, but is not inadvertently displaced or knocked off the forward end of the shank during utilization by reason of the automatic and continuous seating action achieved by the interfit of the key with the dove-tailed slot or keyway.